Initial data commit

Task/Burrows-Wheeler-transform/C-sharp/burrows-wheeler-transform.cs

@@ -0,0 +1,100 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+
+namespace BurrowsWheeler {
+    class Program {
+        const char STX = (char)0x02;
+        const char ETX = (char)0x03;
+
+        private static void Rotate(ref char[] a) {
+            char t = a.Last();
+            for (int i = a.Length - 1; i > 0; --i) {
+                a[i] = a[i - 1];
+            }
+            a[0] = t;
+        }
+
+        // For some reason, strings do not compare how whould be expected
+        private static int Compare(string s1, string s2) {
+            for (int i = 0; i < s1.Length && i < s2.Length; ++i) {
+                if (s1[i] < s2[i]) {
+                    return -1;
+                }
+                if (s2[i] < s1[i]) {
+                    return 1;
+                }
+            }
+            if (s1.Length < s2.Length) {
+                return -1;
+            }
+            if (s2.Length < s1.Length) {
+                return 1;
+            }
+            return 0;
+        }
+
+        static string Bwt(string s) {
+            if (s.Any(a => a == STX || a == ETX)) {
+                throw new ArgumentException("Input can't contain STX or ETX");
+            }
+            char[] ss = (STX + s + ETX).ToCharArray();
+            List<string> table = new List<string>();
+            for (int i = 0; i < ss.Length; ++i) {
+                table.Add(new string(ss));
+                Rotate(ref ss);
+            }
+            table.Sort(Compare);
+            return new string(table.Select(a => a.Last()).ToArray());
+        }
+
+        static string Ibwt(string r) {
+            int len = r.Length;
+            List<string> table = new List<string>(new string[len]);
+            for (int i = 0; i < len; ++i) {
+                for (int j = 0; j < len; ++j) {
+                    table[j] = r[j] + table[j];
+                }
+                table.Sort(Compare);
+            }
+            foreach (string row in table) {
+                if (row.Last() == ETX) {
+                    return row.Substring(1, len - 2);
+                }
+            }
+            return "";
+        }
+
+        static string MakePrintable(string s) {
+            return s.Replace(STX, '^').Replace(ETX, '|');
+        }
+
+        static void Main() {
+            string[] tests = new string[] {
+                "banana",
+                "appellee",
+                "dogwood",
+                "TO BE OR NOT TO BE OR WANT TO BE OR NOT?",
+                "SIX.MIXED.PIXIES.SIFT.SIXTY.PIXIE.DUST.BOXES",
+                "\u0002ABC\u0003"
+            };
+
+            foreach (string test in tests) {
+                Console.WriteLine(MakePrintable(test));
+                Console.Write(" --> ");
+
+                string t = "";
+                try {
+                    t = Bwt(test);
+                    Console.WriteLine(MakePrintable(t));
+                } catch (Exception e) {
+                    Console.WriteLine("ERROR: {0}", e.Message);
+                }
+
+                string r = Ibwt(t);
+                Console.WriteLine(" --> {0}", r);
+                Console.WriteLine();
+            }
+        }
+    }
+}